Field of the Invention
The present invention relates generally to a printer for printing a recorded image such as a video image or the like, as a hard copy in the form of a color photograph, and more particularly to an ink ribbon code reading mechanism for a color video printer of the sublimational thermal-transfer type.
Description of the Related Art
Conventional ribbon code reading mechanisms for an ink ribbon stored in a ribbon cassette in a color video printer include three general types of ribbon code reading mechanisms as follows:
(a) A ribbon code reading mechanism in which, while bringing the head of an ink ribbon from a ribbon cassette into an operative position, an information mark on a ribbon code ring mounted on the shaft of an ink ribbon supply spool in the ribbon cassette is detected by a sensor when the ink ribbon supply spool is rotated while the ink ribbon is being wound;
(b) A ribbon code reading mechanism in which a dedicated motor is used for reading a ribbon code ring, a pendulum gear is rotated by energization of the motor, and a ribbon code is read by a sensor; and
(c) A ribbon code reading mechanism in which, when a print head is moved, a ribbon code ring is rotated by a gear held in ganged relation to the movement of the print head, and a ribbon code is read by a sensor. A ribbon code reading mechanism of this type is shown generally in U.S. Pat. No. 5,290,114.
With the ribbon code reading mechanism (a), the ink ribbon is required to be as long as the angular displacement of the ribbon code ring, and if the ribbon code ring is to be rotated to make several revolutions for increasing the reliability with which the ribbon code is read, then the ink ribbon is also required to be long commensurately with such several resolutions to be made by the ribbon code ring.
The ribbon code reading mechanism (b) requires a motor dedicated to rotate the ribbon code ring. Because a space for installing the motor is needed, it is difficult to reduce the size of the printer, and the cost of the printer is increased.
In the ribbon code reading mechanism (c), when the ribbon code ring is rotated, since the print head is lowered in ganged relation to the ribbon code ring, the ink ribbon is loosened or slackened. With the ink ribbon loosened, the ink ribbon cannot easily be removed from the printer paper. A process of removing the slack from the ink ribbon is time-consuming.
The present invention has been made to solve the above problems of the conventional ribbon code reading mechanisms. It is therefore an object of the present invention to provide a printer in which an ink ribbon is not wound when a ribbon code ring is read, a dedicated motor for rotating the ribbon code ring is not required, and it is possible to rotate the ribbon code ring with the same motor used for moving a print head.
Another problem with conventional video printers is in the ribbon door for inserting and ejecting a ribbon cassette from the printer. Conventional video printers include a cassette holder for holding the ribbon cassette in a predetermined position, and a ribbon door without a lock member for closing the cassette holder. In these devices, the ribbon door may be opened accidentally during printing. To avoid damage to the printer ribbon and other printer components, some conventional printers include a system to stop the printing operation automatically in response to an output of a switch for detecting opening of the ribbon door to avoid damage when the ribbon door is opened.
However, when the ribbon door of these conventional devices is opened accidentally during printing, the quality of the current printing will be reduced if the printing is stopped. On the other hand, damage to the printer components may occur if the printing operation is not stopped upon opening the ribbon door. Thus, it is a further object of the present invention to provide a printer which does not allow accidental opening of the ribbon door during printing operation.